Polypropylene cable jacket compositons with enhanced melt strength and physical properties

ABSTRACT

The present invention is a cable comprising one or more telecommunication or power transmission media or a core of two or more such media, each medium or core surrounded by at least one jacketing or sheathing layer comprising a polypropylene homopolymer or copolymer and having a relaxation spectrum (RSI) and melt flow (MF) such RSI*MF{circumflex over ( )}a is greater than about 12 when a is about 0.5. Significantly, the jacketing or sheathing layer exhibits advantaged extrusion fabrication charateristics, resulting from the propylene polymer having enhanced rheology properties (as demonstrated by its high relaxation spectrum index (RSI)). Additionally, the propylene-based polymer composition of the present invention exhibits relaxtively high melt strength compared to compounds of conventional propylene polymers or ethylene polymers. In fiber optic cable jacketing applications, the present invention advantageously balances low post extrusion shrinkage with high modulus/deformation resistance.

FIELD OF THE INVENTION

This invention relates to telecommunication and power transmissioncables. Specifically, this invention relates to polypropylene-basedcable jackets.

DESCRIPTION OF THE PRIOR ART

Cables for telecommunications and power transmission applicationsgenerally comprise an outer jacket or sheath based on a thermoplasticpolyolefin composition. Additional jacketing applications forthermoplastic polyolefin materials include inner jackets or sheaths. Thejacketing materials often contain carbon black or other additives for UVresistance, thermal oxidative stability, extrusion benefit, or physicalproperty modification. Polyolefin jacketing materials are categorizedbased upon a range of required and preferred application performancetargets.

Desired requirements include flexibility vs. stiffness characteristics,cold bend and cold impact performances, toughness including abrasion,tear and cut-through resistance, environmental compatibility includingenvironmental stress crack resistance (ESCR), weatherability (especiallyfor outdoor sunlight exposures), thermo-oxidative stability, long termaging characteristics, heat deformation, and creep characteristics. Forfiber optic cable applications, crush resistance and post-extrusionshrinkage are also important characteristics.

In addition to the proper balance of required physical properties, a keyperformance for polyolefin jacketing composition is the capability to beextruded at commercial-scale line-speed conditions without formation ofholes or other melt-state instabilities and without the formation of arough surface during the coating process. Therefore, jacketing materialsneed to have sufficient melt strength to avoid holes, tears, or otherdefects in the melt state during the extrusion fabrication process. Agood blemish free and smooth jacketed cable appearance with accuratedimension control is also important. Adequate jacketing material meltstrength is also important to bridge across core imperfections andthereby provide a finished jacketing with uniform surface appearance.Melt strength also contributes to good dimensional control by avoidingmelt sag of the extruded jacket in the fabricating process prior tocooling.

U.S. Pat. No. 5,718,974 describes a cable jacketing made from specificpolyethylene compositions. Most polyolefin jacketing compositionsrequire balancing melt-state properties against a range of physicalproperties.

For example, in optic cable applications, typical polyethylene jacketingmaterials exhibit undesirably high post-extrusion shrinkage and lowerthan desired modulus and deformation resistance. Polypropylene materials(homopolymers and copolymers) would provide increased modulus andreduced post extrusion shrinkage. However, conventional polypropylenematerials lack the melt strength needed for satisfactory performance injacketing “tube-on” extrusion applications and conventional propylenehomopolymers and random copolymers would typically show unsatisfactorycold impact performance for cable jacketing use.

In selected cable jacketing applications, the substantially increasedmelting temperature and heat deformation performance of polypropyleneswould be an advantage. This includes applications such as installationof telecommunication cables in close proximity to steam lines, and powercable use where current overload conditions can overheat the cable.

Another application where polypropylenes would be advantageous is incable applications that use polypropylene for an inner jacket and anethylene-based polymer for an outer jacket. The advantage of thisapplication is that the polypropylene-based inner jacket has arelatively higher melting point than the melting point of theethylene-based outer jacket, thereby leading to a reduced tendency forthe two jacketing layers to fuse during the subsequent melt extrusionapplication of the outer jacket.

However, the poor melt strength of polypropylene based compositions haslimited the utilization of polypropylene for applications, such asthese, despite these substantial advantages of polypropylene in otherproperties.

Therefore, for certain cable jacketing applications, it is desirablethat polypropylene based compositions have the 1) increased meltstrength needed for optimal performance in cable jacketing extrusionprocesses along with 2) required improvements in cold impactperformance. These polypropylene compositions would be preferred forjacketing applications where other inherent polypropylene performancecharacteristics are desired for the most competitive performancebalance. For example, these compositions would be preferred for fiberoptic cable jacketing because they would provide substantially improvedpost extrusion shrinkage and deformation resistance characteristicsversus conventional polypropylene compounds and incumbent polyethylenecompounds.

SUMMARY OF THE INVENTION

The present invention is a cable comprising one or moretelecommunication or power transmission media or a core of two or moresuch media, each medium or core surrounded by at least one jacketing orsheathing layer comprising a polypropylene homopolymer or copolymer andhaving a relaxation spectrum (RSI) and melt flow (MF) such thatRSI*MF{circumflex over ( )}a is greater than about 12 when a is about0.5. Significantly, the jacketing or sheathing layer exhibits advantagedextrusion fabrication characteristics, resulting from the propylenepolymer having enhanced rheology properties (as demonstrated by its highrelaxation spectrum index (RSI)). Additionally, the propylene-basedpolymer composition of the present invention exhibits relatively highmelt strength compared to compounds of conventional propylene polymersor ethylene polymers. In fiber optic cable jacketing applications, thepresent invention advantageously balances low post extrusion shrinkagewith high modulus/deformation resistance.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 shows the “tube-on” or “sleeving” process involved whenstretching a melt tube exiting an extruder to neck in and provide atight jacketing over the cable core.

DESCRIPTION OF THE INVENTION

The invented cable comprises one or more telecommunication or powertransmission media or a core of two or more such media, each medium orcore surrounded by at least one jacketing or sheathing layer comprisinga polypropylene homopolymer or copolymer and having a relaxationspectrum (RSI) and melt flow (MF) such that RSI*MF{circumflex over ( )}ais greater than about 12 when a is about 0.5.

As used herein, the following terms shall have the following meanings:

“Coupling agent” means a chemical compound that contains at least tworeactive groups that are each capable of forming a carbene or nitrenegroup that are capable of inserting into the carbon hydrogen bonds ofCH, CH2, or CH3 groups, both aliphatic and aromatic, of a polymer chain.The reactive groups can thereby couple separate polymer chains to yielda long chain branching structure. It may be necessary to activate acoupling agent with a chemical coagent or catalyst, or with heat, sonicenergy, radiation or other chemical activating energy. Examples ofcoupling agents include diazo alkanes, geminally-substituted methylenegroups, metallocarbenes, phosphazene azides, sulfonyl azides, formylazides, and azides.

Preferred coupling agents are poly(sulfonyl)azides, including compoundssuch as 1,5-pentane bis(sulfonyl azide), 1,8-octane bis(sulfonyl azide),1,10-decane bis(sulfonyl azide), 1,10-octadecane bis(sulfonyl azide),1-octyl-2,4,6-benzene tris(sulfonyl azide), 4,4′-diphenyl etherbis(sulfonyl azide), 1,6-bis(4′-sulfonazidophenyl)hexane,2,7-naphthalene bis(sulfonyl azide), mixed sulfonyl azides ofchlorinated aliphatic hydrocarbons containing an average of from 1 to 8chlorine atoms and from 2 to 5 sulfonyl azide groups per molecule, andmixtures thereof. Preferred poly(sulfonyl azide)s includeoxy-bis(4-sulfonylazidobenzene), 2,7-naphthalene bis(sulfonyl azido),4,4′-bis(sulfonyl azido)biphenyl, 4,4′-diphenyl ether bis(sulfonylazide) and bis(4-sulfonyl azidophenyl)methane, and mixtures thereof. Seealso WO 99/10424. Sulfonyl azides are commercially available or areconveniently prepared by the reaction of sodium azide with thecorresponding sulfonyl chloride. Oxidation of sulfonyl hydrazines withvarious reagents (nitrous acid, dinitrogen tetroxide, nitrosoniumtetrafluoroborate) has also been used.

When a bis(sulfonyl azide) is used, the amount is preferably at leastabout 100 parts per million (“ppm”) based on the total weight of thepropylene polymer. More preferably, the amount is at least about 150ppm. Most preferably, the amount is at least about 200 ppm. For example,when a large change in extrusion and impact properties is desirable ascompared with the base noncoupled impact propylene copolymer, an amountof at least about 300 ppm or 450 ppm is even more preferable.

“Extruders” include devices that (1) extrude pellets, (2) coat wires orcables, (3) form films, foams, profiles, or sheets, or (4) blow moldarticles.

“Impact modified” propylene polymers incorporate an elastomericcomponent (“impact modifiers”) by an in-reactor blend of a propylenepolymer with an elastomeric component or by compounding an elastomericcomponent into the propylene polymer. In the former method, thepropylene polymer and the elastomeric component are produced in one ormore reactors of the same production process. Examples of suitableelastomer materials are EPR rubbers or ethylene-propylene fleximers.Preferably, the impact modifier is a copolymer of ethylene and propyleneor other higher alpha-olefins, such as butene, 4-methyl-1-pentene,hexene, and octene. Optionally, the impact modifier may also contain atleast one diene.

The preferred impact modified polypropylenes have at least about 5weight percent elastomeric impact modifier constituent based on thetotal weight of polypropylene. More preferably, the elastomeric impactmodifier constituent is at least about 9 weight percent. Mostpreferably, the impact modifier content is at least about 13 weightpercent.

When the continuous phase of an impact propylene copolymer is ahomopolymer propylene polymer and the elastomeric phase is comprised ofa copolymer or terpolymer containing monomer units derived fromethylene, the impact propylene copolymer preferably contains at leastabout 5 weight percent, more preferably at least about 7 weight percent,most preferably at least about 9 weight percent —CH2CH2— units derivedfrom ethylene monomer based on the total weight of the propylene phase.Preferably, such an impact propylene copolymer contains less than about30 weight percent, more preferably less than about 25 weight percent,most preferably less than about 20 weight percent —CH2CH2— units derivedfrom ethylene monomer based on the total weight of the propylene phase.

“Impact properties” refer to properties such as impact strength, whichare measured by any means within the skill in the art. Examples ofimpact properties include (a) Izod impact energy as measured inaccordance with ASTM D 256, (b) MTS Peak Impact Energy (dart impact) asmeasured in accordance with ASTM D 3763-93, and (c) MTS total ImpactEnergy as measured in accordance with ASTM D-3763. With regard to coldimpact properties (i.e., properties at temperatures of −20 degrees C. orlower), the ductile-to-brittle transition temperature (“DBTT”) is animportant characteristic. DBTT defines the temperature at which anobject transitions from a predominantly ductile mode of failure to apredominantly brittle mode of failure.

“Impact propylene copolymers” refer to heterophasic propylene copolymerswhere polypropylene or random copolymer polypropylenes are thecontinuous phase and an elastomeric phase is dispersed therein. Theelastomeric phase may also contain crystalline regions, which areconsidered part of the elastomeric phase. The impact propylenecopolymers are prepared by reactively incorporating the elastomericphase into the continuous phase, such that they are a subset of impactmodified propylene polymers. The impact propylene copolymers are formedin a dual or multi-stage process, which optionally involves a singlereactor with at least two process stages taking place therein ormultiple reactors. See E. P. Moore, Jr in Polypropylene Handbook, HanserPublishers, 1996, page 220-221 and U.S. Pat. Nos. 3,893,989 and4,113,802.

Optionally, the impact propylene copolymers may contain impact modifierto further enhance impact properties.

“Rheology properties” refer to the melt-state properties such as theelastic and viscous moduli, the relaxation spectrum or distribution ofrelaxation times, and the melt strength or melt tension which aremeasured by any means within the skill in the art. Deformationresistance typically correlates to the secant or flexural modulusproperties, which are measured in accordance with ASTM D 638 or ASTM D790, respectively.

“Shrinkage properties” refer to the properties of articles, such ascable jackets, which involve the presence, or lack thereof, ofdimensional stability following the extrusion fabrication process. Inwire and cable applications, shrinkage is generally measured parallel tothe cable axis, that is, longitudinally, as the change in a specifiedlength of cable jacketing or sheathing over time. Shrinkage is typicallyevaluated by performing a specified conditioning period in a controlledhigher temperature environment and then measuring the change in theaxial direction. Measurements can be done with the jacket or sheathingeither on or off of a cable core.

As previously-noted, the invented cable comprises one or moretelecommunication or power transmission media or a core of two or moresuch media, each medium or core surrounded by at least one jacketing orsheathing layer comprising a polypropylene homopolymer or copolymer andhaving a relaxation spectrum (RSI) and melt flow (MF) such thatRSI*MF{circumflex over ( )}a is greater than about 12 when a is about0.5.

Based on the response of the polymer and the mechanics and geometry ofthe rheometer used, the relaxation modulus G(t) or the dynamic moduliG′( ) and G″( ) can be determined as functions of time t or frequency,respectively (See Dealy et al, Melt Rheology and Its Role in PlasticsProcessing, Van Nostrand Reinhold, 1990, pages 269 to 297). Themathematical connection between the dynamic and storage moduli is aFourier transform integral relation, but one set of data can also becalculated from the other using the well known relaxation spectrum (SeeWasserman, J. Rheology, Vol. 39, 1995, pages 601 to 625). Using aclassical mechanical model, a discrete relaxation spectrum consisting ofa series of relaxations or “modes”, each with a characteristic intensityor “weight” and relaxation time, can be defined. Using such a spectrum,the moduli are re-expressed as:${G^{\prime}(\omega)} = {\sum\limits_{i = 1}^{N}{g_{i}\quad\frac{\left( {\omega\lambda}_{i} \right)^{2}}{1 + \left( {\omega\lambda}_{i} \right)^{2}}}}$${G^{\prime\prime}(\omega)} = {\sum\limits_{i = 1}^{N}{g_{i}\quad\frac{{\omega\lambda}_{i}}{1 + \left( {\omega\lambda}_{i} \right)^{2}}}}$${G(t)} = {\sum\limits_{i = 1}^{N}{g_{i}\quad{\exp\left( {{- t}/\lambda_{i}} \right)}}}$where N is the number of modes and gi and i are the weight and time foreach of the modes (See Ferry, Viscoelastic Properties of Polymers, JohnWiley & Sons, 1980, pages 224 to 263). A relaxation spectrum may bedefined for the polymer using software such as IRIS™ rheology software,which is commercially available from IRIS™ Development. Once thedistribution of modes in the relaxation spectrum is calculated, thefirst and second moments of the distribution, which are analogous to Mnand Mw, the first and second moments of the molecular weightdistribution, are calculated as follows:$g_{I} = {\sum\limits_{i = 1}^{N}{g_{i}/{\sum\limits_{i = 1}^{N}{g_{i}/\lambda_{i}}}}}$$g_{II} = {\sum\limits_{i = 1}^{N}{g_{i}{\lambda_{i}/{\sum\limits_{i = 1}^{N}g_{i}}}}}$

RSI is defined as gII/gI. Further, nRSI is calculated from RSI asdescribed in U.S. Pat. No. 5,998,558, according tonRSI=RSI*MFR{circumflex over ( )}awhere MFR is the polypropylene melt flow rate as measured using the ASTMD-1238 procedure at 230° C. and 2.16 KG weight, and a is approximately0.5. The nRSI is effectively the RSI normalized to an MFR of 1.0, whichallows comparison of rheology data for polymeric materials of varyingmelt flow rates. RSI and nRSI are sensitive to such parameters as apolymer's molecular weight distribution, molecular weight, and featuressuch as long-chain branching and crosslinking. The higher the value ofnRSI, the broader the relaxation time distribution.

Propylene polymers useful in the present invention may be made usingZiegler-Natta catalyst, constrained geometry catalyst, metallocenecatalyst, or any other suitable catalyst system.

Preferentially, the propylene polymers of the present invention arecoupled, which coupling can be achieved in several ways. The couplingcan be carried out during the polypropylene polymerization process viaspecialized catalyst, co-reactive agents, and other means known to oneof ordinary skill in the art. Alternatively, the coupling can be carriedout in post polymerization steps. Examples of suitablepost-polymerization steps include coupling the polymers in an extruderusing a coupling agent or treating the propylene polymers in an e-beamprocess.

Melt flow rate is an important feature to consider when selecting thebase noncoupled propylene polymer for coupling. It is important to yielda coupled polymer with sufficient melt flow rate for processing.

Furthermore, the coupled polymer may be blended with other propylenepolymers, including homopolymer propylene polymers, random propylenecopolymers and other impact propylene polymers, or other polyolefins tomake thermoplastic olefins (TPO's) or thermoplastic elastomers (TPE's).Optionally, the other propylene polymers or polyolefins may be coupledwith coupling agents.

It is possible to quantify the effect of coupling on the long-relaxationtime behavior of the polymer by using the relaxation spectrum index(RSI). The RSI represents the breadth of the relaxation timedistribution, or relaxation spectrum.

In one embodiment of the present invention, the polypropylene resinshave sufficient coupling to provide an absolute RSI value of at leastabout 12. More preferably, a RSI of at least about 15 is desired. Evenmore preferably, the RSI is of at least about 18, and in some instances,the RSI is most preferably at least about 20.

In a preferred embodiment of the current invention, the coupling agentis added to produce a coupled polypropylene homopolymer or copolymer,having an RSI preferably at least about 1.3 times that of a comparablenoncoupled propylene polymer. More preferably, the RSI at least about1.5 times. A comparable noncoupled propylene polymer is the base polymerused to make the coupled propylene polymer.

In a more preferred embodiment, coupling of an impact modifiedpropylene-based polymer increases the melt strength of the polymer.Typically the impact properties of the resulting cable jacket are alsoenhanced as compared to those properties of a cable jacket comprising acomparable noncoupled impact modified propylene-based polymer.Preferably, the coupled impact modified propylene polymer resins have amelt strength of at least about 8 centiNewtons, more preferably a meltstrength of at least about 15 cN, and most preferably a melt strength ofat least about 30 cN.

Alternatively, the invention can be characterized by the followingformula:Y≧1.25, in whichY=the ratio of the melt strength of the coupled propylene resin comparedto the melt strength of the comparable noncoupled polypropylene.Preferably, in this aspect, Y is at least about 1.5; more preferably, Yis at least about 2; most preferably, Y is at least about 5.

The impact modification can be achieved by the use of impact propylenecopolymers or by melt mixing of a wide range of elastomeric materialsinto the propylene polymer, either before or after coupling isaccomplished. A combination of coupled impact-modified propylenepolymer, for example, with an elastomeric component can also be used.

The propylene-based polymer composition preferably is impact modified toprovide the cold impact performance needed for most cable jacketingapplications. Preferably, the propylene polymer composition exhibits aDBTT of less than −5° C., more preferably less than −10° C., furthermore preferably less than −15° C., most preferably less than −20° C.

Additionally, the articles made from the compositions and tested inaccordance with ASTM D 256 preferably exhibit an IZOD impact strength ofat least 0.7 ft-lb/in, more preferably at least 1.5 ft-lb/in, mostpreferably at least 2.0 ft-lb/in. Further, the propylene-based polymercompositions preferably will exhibit a 2 percent secant modulus of atleast 90,000 pounds per square inch (psi), more preferably at least100,000 psi, further more preferably at least 110,000 psi, mostpreferably at least 120,000 psi when tested in accordance with ASTM D638. Finally, jackets made from the propylene-based polymer compositionof the invention preferably exhibit post extrusion shrinkage of lessthan about 2.7 percent, more preferably less than about 2.5 percent,further more preferably less than about 2.3 percent and most preferablyless than about 2.0 percent shrinkage measured along the longitudinalaxis.

Impact properties for the coupled propylene polymers comprising thepresent invention are typically enhanced versus comparable conventionalpropylene polymers. Furthermore, cable jackets formed from the coupledpropylene resins of the present invention advantageously maintain thehigh modulus and deformation characteristics, for example, as measuredby flexural or secant modulus, of the comparable cable jackets formedfrom non-coupled versions of the same propylene polymers.

The jacketing and/or sheathing layers can be either foamed ornon-foamed. In one particular preferred embodiment, the cable iscomprised of an inner jacketing or sheathing layer and an outerjacketing or sheathing layer. Preferably, the inner jacketing orsheathing layer is foamed. Also preferably, the inner jacketing orsheathing layer is comprised of a propylene-based polymer while theouter jacketing or sheathing layer is comprised of an ethylene-basedpolymer

The propylene polymer compositions can also contain non-halogenated orhalogenated flame retardant additives. Suitable non-halogenated flameretardant additives include metal hydrates, red phosphorus, silica,alumina, titanium oxides, talc, clay, organo-modified clay, zinc borate,antimony trioxide, wollastonite, mica, silicone polymers, phosphateesters, hindered amine stabilizers, ammonium octamolybdate, intumescentcompounds, and expandable graphite. Suitable halogenated flame retardantadditives include decabromodiphenyl oxide, decabromodiphenyl ethane,ethylene-bis(tetrabromophthalimide), and1,4:7,10-Dimethanodibenzo(a,e)cyclooctene,1,2,3,4,7,8,9,10,13,13,14,14-dodecachloro-1,4,4a,5,6,7,10,10a,11,12,12a-dodecahydro-).

The propylene polymer compositions of the present invention can alsocontain fillers such as calcium carbonate. Additionally, nucleatingagents may be utilized. These nucleating agents can increase the rate atwhich the resins crystallize and enhance the physical properties.However, in some instances, the presence of a nucleating agent in acoupled impact propylene copolymer, may reduce the balance of the impactand toughness properties of a cable jacket formed from the coupledimpact propylene copolymer. NA-11, which is available from Asahi DenkaCorporation, is an example of a useful nucleating agent. In addition,the composition may contain other additives such as antioxidants,stabilizers, blowing agents, carbon black, pigments, processing aids,peroxides, cure boosters, and surface active agents to treat fillers maybe present.

A comparison of key jacketing performance requirements for compositionsbased on polyethylene, conventional propylene-based polymer (CategoryI), and coupled propylene-based polymer (Category II) is provided asTable 1 below. A third category (Category III) comprises coupledpropylene-based polymer compositions that include an additionalelastomeric component. The Category III compositions demonstrate theeffect of adding additional elastomer to the composition after couplingthe propylene-based polymer.

Performance in each key property category are qualitatively ranked fromunacceptable (−−, −), to acceptable but not preferred (0), to advantaged(+, ++), and to very advantaged (+++, ++++) for the various materialoptions shown. This matrix illustrates the overall advantage provided byhigh-melt-strength polypropylene compositions for certain jacketingapplications. TABLE 1 Comparison of Jacketing Performances High MeltStrength Conventional High Melt Strength Polypropylene with PolyethylenePolypropylene Polypropylene Additional Impact Modifier Desired JacketingProperty LLDPE HDPE Homo- Random Impact Homo- Random Impact Homo- RandomImpact Low Post Extrusion Shrinkage − 0 ++++ +++ +++ +++ ++ ++ ++ + +High Modulus/Deformation −− 0 +++ + ++ +++ + ++ ++ 0 + Resistance GoodLow Temperature Impact ++++ ++ −− − + − 0 ++ + ++ +++ HeatDeformation/Melt Point −− − ++ + ++ ++ + ++ ++ + ++ above 130 degrees C.Extrudability/Melt Strength + + − − − ++ ++ ++ ++ ++ ++

EXAMPLES

The following non-limiting examples illustrate the invention.

Comparative Examples 1-5 and Examples 6-12

The following propylene polymers were used to prepare the exemplifiedcompositions: (a) C105-02 impact propylene copolymer; (b) D111.00 impactpropylene copolymer; (c) C104-01 impact propylene copolymer; (d) C107-04impact propylene copolymer; (e) 6D20 random propylene copolymer. Also,the following jacketing compositions were evaluated in the examples: (a)DGDD-6059 jacketing compound and (b) DBDA-6318 jacketing compound. Eachpropylene polymer and jacketing lo compound is available from The DowChemical Company.

C105-02 is a high impact propylene copolymer, having a melt flow rate of1.5 g/10 min and an ethylene content of 16 wt percent. D111.00 is amedium impact propylene copolymer, having a melt flow rate of 0.8 g/10min and an ethylene content of 9 wt percent. C104-01 is a medium impactpropylene copolymer, having a melt flow rate of 1.1 g/10 min and anethylene content of 9 wt percent. C107-04 is a medium impact propylenecopolymer, having a melt flow rate of 4.0 g/10 min and an ethylenecontent of 9 wt percent. 6D20 is a random propylene copolymer, having amelt flow rate of 1.8 g/10 min. Comparative Examples 1-5 were preparedwith C105-02, D111.00, C104-01, C107-04, and 6D20 respectively.

One or more of the exemplified compositions were prepared using4,4′-oxy-bis-(sulfonylazido)benzene (“DPO-BSA”) as a coupling agent.Some of the exemplified compositions also contained Irganox 1010™tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydro-cinnamate)]methane, Irgafos 168™tris(2,4-ditert-butylphenyl)phosphite, and FX-5911X™ processing aid.Irganox 1010 and Irgafos 168 are available from Ciba Specialty ChemicalsInc. FX-5911X is an HFP/VDF/TFE polymer, which is available from DyneonLLC, a wholly owned subsidiary of 3M Corporation.

As described below, the coupling agent was also prepared as amasterbatch in Affinity EG-8200™ polyethylene or Profax 6501polypropylene. Affinity EG-8200™ polyethylene is an ethylene/octenecopolymer with a melt index of 5.0 grams/10 minutes and a density 0.87grams/cubic centimeter, which is available from The Dow ChemicalCompany. Profax 6501 is propylene homopolymer, having a melt flow rateof 4 g/10 min, and available from Montell USA, Inc.

DPO-BSA Master Batch 1 was prepared in Affinity EG-8200™ polyethylene toyield 5 weight percent concentrate. DPO-BSA Master Batch 2 was preparedin Profax 6501 such that when 5 weight percent of the masterbatch wasadded to a composition, the masterbatch provided a 200-ppm amount ofDPO-BSA. DPO-BSA Master Batch 3 was prepared in Profax 6501 such thatwhen 0.9 weight percent of the masterbatch was added to a composition,the masterbatch provided a 180-ppm amount of DPO-BSA. DPO-BSA MasterBatch 4 was prepared in Profax 6501 such that when 2 weight percent ofthe masterbatch was added to a composition, the masterbatch provided a200-ppm amount of DPO-BSA.

For Examples 6, 7, and 9, the exemplified compositions were extrudedthrough an 11-barrell Werner & Pfleiderer ZSK40 twin screw extruder at afeed rate of 250 lbs/hr, a screw speed of 300 rpm, and a targettemperature profile of 180/190/200/200/210/220/230/240/230/240/240degrees C. (from feed inlet to die). For Example 8, the mixture wasextruded through a 9-barrell Werner & Pfleiderer ZSK92 mm twin screwextruder at a feed rate of 2900 lbs/hour, a screw speed of 400 rpm, anda target temperature profile of 25/25/25/200/200/240/240/240 degrees C.(from feed inlet to die).

For Example 10, the mixture was extruded at conditions typical ofprocessing a 0.8 melt flow rate impact copolymer. For Example 11, themixture was extruded at conditions typical of processing a 1.2 melt flowrate impact copolymer. For Example 12, the mixture was extruded througha 9-barrell Century ZSK40 twin screw extruder at a feed rate of 130lbs/hr, a screw speed of 220 rpm, and a target temperature profile of80/80/200/220/230/240/240/240 degrees C. (from feed inlet to die).

When a master batch of DPO-BSA was used for an Example, the masterbatchwas fed simultaneously with the propylene polymer and the otheradditives into the feed hopper of the extruder.

In the following Table 2, the symbol “(d)” indicates that the DPO-BSAwas added via direct addition rather than via a masterbatch. If amasterbatch was used, the corresponding box was filled with a “Y”. TABLE2 Compositions Component C-1 C-2 C-3 C-4 C-5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex.10 Ex. 11 Ex. 12 C105-02 Y Y Y Y D111.00 Y Y Y C104-01 Y Y C107-04 Y Y6D20 Y DPO-BSA (ppm)  450 (d)  200  180  200 150 (d)  200 (d)  200DPO-BSA (MB-1) Y DPO-BSA (MB-2) Y DPO-BSA (MB-3) Y DPO-BSA (MB-4) YMineral Oil (ppm) 2000 Irganox 1010 (ppm) 1000 1000 1500 600 2300 1000Irgafos 168 (ppm) 1000 1000 1000 600  600 1000 FX-5911X  300 Calciumstearate 500  500

Tables 3 and 4 report the notched Izod values for Comparative Examples 1and 2 and Examples 6, 7, and 9. Each notched Izod was measured followingASTM Method D-256 as described in Section 8: Plastics 1997. Theedge-gated plaques were injection molded. The required test samples werecut parallel and perpendicular to the polymer injection flow direction.After notching, samples were tested with the orientation of the notchrespectively perpendicular and parallel to the polymer injection flowdirection. A ductile break is indicated with “(b)” following thereported value. TABLE 3 Perpendicular Notched Izod With NotchPerpendicular to Flow (J/m) Temp. (° C.) Comp. Ex. 1 Ex. 6 Ex. 7 Comp.Ex. 2 Ex. 9 20 801 (b) 15 694 (b) 10 534 (b) 368 (b) 5 160 342 (b) 0 160587 (b) 747 (b) 171 641 (b) −5 160 187  85 502 (b) −10 107 641 (b) 171 91 379 (b) −15  53 214 −20  53 214 112  96 240 (b) −25  75

TABLE 4 Parallel Notched Izod With Notch Parallel to Flow (J/m) Temp. (°C.) Comp. Ex. 1 Ex. 6 Ex. 7 Comp. Ex. 2 Ex. 9 23 235 20 587 (b) 15 214176 10 214 336 (b) 160 5 107 208 117 0 107 587 (b) 149  85 550 (b) −5240 (b) −10 480 (b) 112  75 117 −15 160 −20 107 101  75  96

Melt flow rate (MFR) for Comparative Examples 1-5 and Examples 6-12 wasmeasured at 230° C. with a 2.16-kg weight according to the method ofASTM D1238.

Rheology measurements were done via dynamic oscillatory shear (DOS)experiments conducted with the controlled rate WeissenbergRheogoniometer, commercially available from TA Instruments. Standard DOSexperiments were run in parallel plate mode under a nitrogen atmosphereat 200 or 230 degrees C. Sample sizes ranged from approximately 1100 to1500 microns in thickness and were 4 centimeters in diameter. DOSfrequency sweep experiments covered a frequency range of 0.1 to 100sec-1 with a 2 percent strain amplitude. The TA Instruments rheometercontrol software converted the torque response to dynamic moduli anddynamic viscosity data at each frequency. Discrete relaxation spectrawere fit to the dynamic moduli data for each sample using the IRIS™commercial software package, followed by the calculation of RSI valuesas described earlier.

Melt strength for all the samples was measured by using a capillaryrheometer fitted with a 2.1-mm diameter, 20:1 die with an entrance angleof approximately 45 degrees. After equilibrating the samples at 190° C.for 10 minutes, the piston was run at a speed of 1 inch/minute. Thestandard test temperature is 190° C. The sample is drawn uniaxially to aset of accelerating nips located 100 mm below the die with anacceleration of 2.4 nm/sec². The required tensile force is recorded as afunction of the take-up speed of the nip rolls. The maximum tensileforce attained during the test is defined as the melt strength. In thecase of polymer melt exhibiting draw resonance, the tensile force beforethe onset of draw resonance was taken as melt strength. TABLE 5 MeltFlow Rate, Rheology Values, and Melt Strength Property C. 1 Ex. 6 Ex. 7Ex. 8 C. 2 Ex. 9 Ex. 10 C. 3 Ex. 11 C. 4 Ex. 12 C. 5 MFR 1.5 1.0 0.8 0.31.1 0.5 4.0 3.6 1.8 RSI 20.1 42.1 8.7 5.0 14.5 8.6 nRSI 20.1 23.1 9.110.0 27.5 11.5 Melt strength 5 64 8 7.9 70 (centiNewtons) Y 12.8 1.6 8.9

Comparative Examples 13 and 14 and Example 15

Comparative Example 13 was prepared using DGDD-6059 jacketingcomposition. DGDD-6059 is a 0.932 grams/cubic centimeter densitycomposition made from a base ethylene/butene copolymer having a densityof 0.921 grams/cubic centimeter mixed with about 2.5 wt percent carbonblack.

Comparative Example 14 was prepared using DBDA-6318 jacketingcomposition. DBDA-6318 is a 0.954 grams/cubic centimeter densitycomposition made from a base resin having (1) about 90 wt percentethylene/hexene copolymer having a density of 0.945 grams/cubiccentimeter and (2) about 10 wt percent ethylene/butene copolymer havinga density of 0.921 grams/cubic centimeter mixed with about 2.5 wtpercent carbon black.

Example 15 was prepared using a coupled impact modified propylenepolymer, having a melt flow rate of 1.0 grams/ 10 minutes. Theexemplified high melt strength impact modified propylene polymercomposition contained an amount of carbon black comparable to the amountpresent in the DGDD-6059 and DGDA-6318 compositions.

Table 6 shows performance data for a conventional LLDPE (ComparativeExample 13), a low-shrink HDPE (Comparative Example 14), and a coupledimpact modified propylene polymer (Example 15).

The post extrusion shrinkage modeled extrusion of 0.124 inch outsidediameter specimen on 14-gauge wire (0.064 inch) metallic conductor. Thespecimens were aged 24 hours at room temperature and removed from theconductor. The shrinkage was measured after aging at 100° C. for 24hours. TABLE 6 Post Extrusion Shrinkage and Secant Modulus PropertyComp. Ex. 13 Comp. Ex. 14 Example 15 Polyethylene Melt Index 0.8 0.8 PPMelt Flow Rate 1.0 Post Extrusion 3.34 2.98 1.71 Shrinkage (%) SecantModulus (psi) 42,000 90,000 130,000

1. A cable comprising one or more telecommunication or powertransmission media or a core of two or more such media, each medium orcore surrounded by at least one jacketing or sheathing layer comprisinga polypropylene and having a relaxation spectrum (RSI) and melt flow(NE) such that RSI*MF{circumflex over ( )}a is greater than about 12when a is about 0.5.
 2. The cable of claim 1 wherein the polypropylenebeing coupled.
 3. The cable of claim 2 wherein the coupled polypropylenebeing characterized by the following formulaY>1.25, wherein: Y=a ratio of a melt strength of the coupledpolypropylene to the melt strength of the comparable noncoupledpolypropylene.
 4. The cable of claim 1 wherein the polypropylene is animpact modified propylene copolymer.
 5. The cable of claim 4 wherein theimpact modified propylene copolymer comprises a continuous phase and anelastomeric phase, wherein the elastomeric phase being present in anamount of at least about 9 weight percent of the impact modifiedpropylene copolymer.
 6. The cable of claim 1 wherein the polypropylenebeing a foamed propylene-based polymer.
 7. The cable of any of thepreceding claims wherein the cable having an inner jacketing orsheathing layer and an outer jacketing or sheathing layer, wherein theinner layer being the jacketing or sheathing layer characterized inclaim 1 and the outer layer comprising an ethylene polymer.
 8. A cablecomprising one or more telecommunication or power transmission media ora core of two or more such media, each medium or core surrounded by atleast one jacketing or sheathing layer comprising a coupled impactmodified propylene copolymer being characterized by the followingformulaY≧1.25, wherein: Y=a ratio of a melt strength of the coupledpolypropylene to the melt strength of the comparable noncoupledpolypropylene, comprising a continuous phase and an elastomeric phase,wherein the elastomeric phase being present in an amount of at leastabout 9 weight percent of the impact modified propylene copolymer, andhaving a relaxation spectrum (RSI) and melt flow (MF) such thatRSI*MF{circumflex over ( )}a is greater than about 12 when a is about0.5.
 9. A cable comprising one or more telecommunication or powertransmission media or a core of two or more such media, each medium orcore surrounded by at least one jacketing or sheathing layer comprisinga polypropylene homopolymer or copolymer and having a melt strengthgreater then about 8 centiNewtons.